Selecting data from database based on selection from another table - php

Question

Newby to php / sql so be kind to my ignorance.
On page index.php I have a navigation menu that retrieves options from table car_category, column car_type.
If user selects option from navigation, it takes him to another page where he should see list of entries selected from column car_review_details, coming from another table, car_review.
First function executes on index.php and retrieves the data from table car_category:
function list_type (){
global $conn, $sql, $test;
$test = "SELECT car_type FROM `car_category` WHERE car_type IS NOT NULL AND car_type <> ''";
$result = mysqli_query($conn, $test);
if (!$result){
die("failed");
}
while ($row = mysqli_fetch_assoc($result)){
echo "<a href='car_review.php?subject=";
echo urlencode ($row["car_type"]);
echo "'>";
echo $row ["car_type"];
echo "</a>";
echo "<br>";
}
}
The function above works fine.
Now, on page care_review.php I would like display the data from column car_review_details. The tables car_category and car_review have the column catID which should determine which data gets selected from table car_review, based on the selected link in page index.php
Code for function on page car_review.php looks as following:
function car_style(){
global $conn;
$details = "SELECT *
FROM `car_category`
INNER JOIN `car_review`
ON `car_category`.`catID` = `car_review`.`catID`
WHERE `car_category`.`catID` = $row ['catDesc']";
$result = mysqli_query($conn, $details);
if (!$result){
die("failed");
}
while ($row_1 = mysqli_fetch_assoc($result)){
echo ($row_1["car_review_details"]);
echo "<br>";
}
}
How do I go about echoing data from column car_review_details based on selection from function list_type ().
Many thanks for your feedback.